Boil the sugar and water until all of the sugar has dissolved.
Add the cherries and cinnamon stick and let the mixture simmer for 8 to 10 minutes, or until the cherries soften considerably.
Remove the pan from the heat and add the liquor.
Once cooled, the cherries and juice (cinnamon stick removed) can be stored in a clean jar in the refrigerator for up to two weeks, although I've never even come close to reaching that deadline before they've disappeared.
The cherries are fabulous, as previously mentioned, as a garnish for a Kir Royal, but in my house we have been known to stick a fork directly into the jar straight from the fridge after dinner.